Can I just carry my national driving permit?

If you are not a resident (i.e. you are on a tourist visa or exemption of visa), you only need your national driving permit to be able to drive in Thailand. So, if you are visiting Thailand as a tourist and you want to rent a car for just a few days, you just need to carry the driving permit you obtained in your home country. This is clearly indicated in the Motor Vehicle Act:

Section 42-2
In case there’s a treaty between the Thai government and a foreign government regarding mutual acceptance of driver’s license, an alien who doesn’t have an immigrant visa may drive a motor vehicle with a driver’s license issued by such a foreign government, or an automobile association authorized by such a foreign government.

Do I need to get an international driving license?

An international driving permit (IDP) can be obtained in your home country. Basically, it is a translation in English of your original driving license, so if your national driving license is not in English, it can save some hassle with the police if you can produce an IDP.

Be careful of the period of validity of your IDP, as it can be as short as three months, no longer than three years in any case, and no longer than the period of validity of your national permit. Besides, to be valid, the IDP must be carried together with the national permit.

In any case, to determine if you need an IDP or not, you should also read in details what any contract says, for instance your travel insurance or any vehicle rental agreements.

Who needs a Thai driving license?

People who are residents in Thailand (on a non-immigrant visa) are required to obtain a Thai driving license in order to legally drive a car or a motorbike.

should you drive on thai roads as a tourist you need an international driving license .. ONLY the 9 asian countries are exempt from this ..The comment in paragraph 1 that you only need your driving permit from your own country is total nonsence [highway police volunteer

Alf Haupt is correct, you need an international one, as Thailand does not have treaties with any country except the ASEAN ones.
Also an international one is only valid for 6 months in a row in thailand, no matter if the actual document has 3 years on it, you cannot drive more than 6 months in a row on it, if longer you need to get a local license!

The IDP's issued for three years are from the 1968 agreement. Neither Thailand or any of the English speaking countries ratified the 1968 agreement.
IDP's that are valid in Thailand are the ones issued IAW the 1949 agreement which are issued for only one year.
"he must carry documents specified by the treaty.." makes it pretty clear that the IDP is required unless, as already mentioned, the home country license is accepted by a different agreement such as the ASEAN agreement

Finally a website giving the correct information, and what happens? Some people find it necessary to give incorrect information here.
Driving in thailand dot com is correct.
Not about the video on the homepage though. It states 'young girl driving motorbike in Thailand, but the video is clearly not Thai.

Dear sir,
I would like to visit Thailand and rent a car for the trip. I have a international driver licence from Hong Kong with the type of private car and light goods vehicle. Could I rent the car with 10 seats in Thailand?
Thanks & regards,
Chris Leung

im married to a thai with 2 children 1 age 16 1 age 9 can i apply for a marriage visa but i live in the uk ang go to thailand 4 times a year could u advise me on the visa that would be better for me i have marriage cartificate and birth certificates for my children thank you my tel 07455331608

YOU CAN NOT DRIVE IN PATTAYA THAILAND WITH YOUR INDIAN LICENCE. POLICE WILL TAKE 400 BAHT AS PENALTY. ONLY INTERNATIONAL DRIVING LICENCE IS VALID IN PATTAYA NOW. I MYSELF FACED IT LAST MONTH N NEED TO PAY 400 BAHT IN POLICE STATION.
KINDLY DONT DRIVE WITH INDIAN LICENCE IN PATTAYA

I was recently fined 400baht, stopped by police, using a valid New Zealand driving licence, driving rented car ,for 3 days.
My driving licence was written totally in English language, as its out main language here in New Zealand.
I was told before my departure fron NZ that no IDP was required, as it only applied to non English written driving licences.
Michael

Michael, you have encountered the rabble that masquerades as a police force. The legal position is that you do not require an IDP, you merely have to have your NZ licence. You were the subject of a shakedown, either due to corruption or ignorance.

I have rented a car from international agencies (Budget) and local (Thai rental cars) and the only thing I showed was my US drivers license and there was no problem. Perhaps an international permit is preferred and could avoid some drama but it is NOT required.

HELLO EVERYBODY....ITS NOT STILL CLEAR. I HAVE MY INDIAN DRIVING CARD LICENSE IN ENGLISH AND PLANING TO DRIVE FROM BANGKOK TO HUA HIN AND BACK. MY RENTAL CAR COMPANY STATED THEY ARE OK WITH INDIAN LICENSE AS ITS IN ENGLISH
PLEASE UPDATE IF I REQUIRE IDP ...THANKS